Pop-up stock spam
         

Spammers using the Storm worm botnet appear to have launched a multi-format campaign to promote penny stock Hemisphere Gold Inc (HPGI.PK). In addition to sending plaintext and PDF spam promoting the stock, the operators have also apparently downloaded new software to infected Windows machines that causes pop-up messages advertising HPGI.PK to appear on victims' computers. Joe Stewart at SecureWorks, who has made an extensive study of Storm, has published a picture of the pop-up. Text shown in the pop-up matches text sent in the plaintext and PDF versions.
         

http://www.spamnation.info/blog/archives/2007/11/popup_stock_spam.html